Process for spinning nitrocellulose solutions



No Drawin g.

To all whom it my concern:

Be it known that l, ACHILLE Daren, residing at Londerzeel, Province of Brabant, Kingdom of Belgium, have invented certain new and useful improvements in Processes for Spinning Nitrocellulose Solutions, of which the following is a specification.

My invention relates to a process for spinning nitrocellulose solutions for the manu facture of artificial silk, artificial horse-hair, artificial straw, film bands and other simi lar products.

Actually, artificial silk and similar products based upon the use of nitrocellulose are spun in free air; the nitrocellulose solution is forced through a suitable orifice at the issue of which, owing to their tension of vapor, the solvents of the nitrocellulose, generally sulfuric ether and ethylic alcohol, vaporize and dilute in the atmosphere.

This process has several inconveniences:

The recovering of the solvents is very diliicult on account of their dilution in a great volume of air: if it is proposed to absorb the solvents in towers in which sulfuric acid is injected, it is necessary to use concentrated cold sulfuric acid without possibility of avoiding great losses at the outlet of the tower. On the other hand, the spinning in air causing the coagulation of. the outer shell or envelop of the filament before the central portion be evaporated, the filament of artificial silk, manufactured with a solution of nitrocellulose, always presents an irregular section and is generally not so smooth and so bright as filaments of artificial silk manufactured accordin to other processes.

l y improved process avoids these inconveniences.

According to this process, nitrocellulose containing from 25 to 30% of water or even more, is dissolved in the ordinary solvents, sulfuric ether and ethylic alcohol, and the solution is directly coagulated in a bath of sulfuric acid while being forced through a suitable spinning orifice. A filament of nitrocellulose is thus formed while the ether and the alcohol, combining with the sulfuric acid of the bath, are recovered simultane ously during the spinning operation. The rate of coagulation is very great on account of the great power of absorption of sulfuric acid for ether and alcohol. In order to secure a complete absorption of the solvents in the coagulating bath, the length of this Serial lilo. 325,718.

wound as usually on a suitable bobbin. The

filaments issuing from the coagulating bath carry with them a sullicient quantity of liquid to obtain that, during the winding operation, they remain subjected to the action of the coagulating bath. If necessary the bobbins can be directly sprinkled either with sulfuric acid of the same composition as that of the coagulating bath or with alcohol, in a more or less diluted state, or with a solution of a salt or even with pure water.

The coagulating bath is preferably maintamed at a given concentration of monohydrate while the concentration of ether and alcohol is also maintained at an invariable height. The concentration of the bath in monohydrate may vary in large limits: with a nitrocellulose originally dry, the concentration may be lowered to 30%; with a nitrocellulose containing originally from 25 to 30% of water, good results have been obtained with a concentration of to of monohydrate; any intermediary concentration between 30 and 75% of monohydrate can be used. Itis however necessary that the coagulating bath always contain a minimum 0 25% of water so as to avoid any decomposition of the nitrocellulose. The coagulating bath is used at the temperature of the atmosphere; its temperature may however be lowered so as to reduce the little tension of vapor which the ether and the alcohol still possess in this bath.

A part of the coagulating liquid can be regularly withdrawn from the bath and this liquid is then subjected to a distillation which is assisted by an addition of water; this distillation gives then on the one hand, ether and alcohol and on the other hand,

weakened sulfuric acid which can be brought to a suitable degree by aid of the usual process of concentration. The liquids coming from the sprinkling of the bobbins are treated in a similar manner.

The degree of hydration of the nitrocellulose at the origin may vary in large limits on account of the ailinity for the water of the sulfuric acid contained in the bath.

Whereas a solution prepared by aid of a nitrocellulose containing 30% of water always gives a milky silk without bril Patented May 11(0), ilttftiti when it is spun in free air such an liancy totally avoided with my inconvenience is im roved process.

itherto it has been proposed for a similar purpose in spinning of nitrocellulose solutions to make use of a bath of alcohol, more or less diluted, or more or less heated. But such a coagulating bath has a very slow action and requires a very little speed of spinning in combination with very long baths; the product however has no brilliancy and the recovering of the solvents is difiicult on account of the high tension of V3. or of the solvents in such a bath.

y improved process makes it also possible to use, for the dissolution of the nitrocellulose, solvents which otherwise are unsuitable for the spinning in free air either in view of their low tension of vapor or for any other reason. Acetone and acetic ether, for example, are two good solvents of nitrocellulose but the products obtained by evaporating in free air a solution contaimng one of these solvents, are milky, opacous and without brilliancy whereas the same solution gives a transparent, smooth and brilliant product when it is coagulated in a bath of sulfuric acid. 4

Solvents, such as mixtures of acetone and ethylic alcohol or acetic ether and ethylic alcohol have further the advantage that, owing to the low tension of vapor of their components at the usual temperatures, the losses during the dissolution and the filtration are very reduced while the recovering of the solvents during the spinning operation is greatly facilitated.

It is essential in the above described process that the solution of nitrocellulose be coagulated in the bath of sulfuric acid at p the moment of issue from the spinning apparatus in such a manner that the solvents filament however be first spun in free air and then brought in sulfuric acid as it has already been proposed, a great part of the solvents should be evaporated before its immersion in the bath and this partial evaporation of the solvents would produce all the inconveniences already described which are inherent to the spinning in free air.

What I claim is: 1

1. In the process of spinning nitrocellulose solutions for the manufacture of artificial silk, artificial horse-hair, artificial straw, film-bands and similar products, the improvement consisting in coagulating the filament in a bath of sulfuric acid at the issue of the spinning orifice.

' 2. The process of spinning nitrocellulose solutions consisting in preparing a solution of nitrocellulose, forcing said solution through a spinning orifice and coagulating the filament at its issue from the spinning orifice in a bath of sulfuric acid, without contact of. said filament with the air.

' 3. The process of spinning nitrocellulose solutions consisting in preparing a solution of nitrocellulose, forcing said solution through a spinning orifice, said spinning orifice being placed in a bath of sulfuric acid, and directing the filament horizontally in the bath of sulfuric acid at its issue from the spinning orifice.

In testimon whereof I afiix my signature in presence 0 two witnesses.

AGHILLE DRYEN.

Witnesses:

JACQUES Bonn, F. P. ZABEUE. 

